STROBE Statement—Checklist of items that should be included in reports of cross-sectional studies

Title and abstract

ItemNo1

Recommendation(a) Indicate the study’s design with a commonly used term in the title or the abstract(b) Provide in the abstract an informative and balanced summary of what was done
and what was found

Introduction
Background/rationale

2

Explain the scientific background and rationale for the investigation being reportedObjectives

3

State specific objectives, including any prespecified hypotheses

Methods
Study design

4

Present key elements of study design early in the paperSetting

5

Describe the setting, locations, and relevant dates, including periods of recruitment,
exposure, follow-up, and data collection

Participants

6(a) Give the eligibility criteria, and the sources and methods of selection ofparticipants

Variables

7

Clearly define all outcomes, exposures, predictors, potential confounders, and effectmodifiers. Give diagnostic criteria, if applicable

Data sources/measurement

8*For each variable of interest, give sources of data and details of methods ofassessment (measurement). Describe comparability of assessment methods if there ismore than one group

Bias

9

Describe any efforts to address potential sources of bias

Study size

10Explain how the study size was arrived at

Quantitative variables

11Explain how quantitative variables were handled in the analyses. If applicable,
describe which groupings were chosen and why

Statistical methods

12(a) Describe all statistical methods, including those used to control for confounding(b) Describe any methods used to examine subgroups and interactions(c) Explain how missing data were addressed(d) If applicable, describe analytical methods taking account of sampling strategy(e) Describe any sensitivity analyses

Results
Participants

13*(a) Report numbers of individuals at each stage of study—eg numbers potentiallyeligible, examined for eligibility, confirmed eligible, included in the study,
completing follow-up, and analysed(b) Give reasons for non-participation at each stage(c) Consider use of a flow diagram

Descriptive data

14*(a) Give characteristics of study participants (eg demographic, clinical, social) andinformation on exposures and potential confounders(b) Indicate number of participants with missing data for each variable of interest

Outcome data

15*

Report numbers of outcome events or summary measures

Main results

16(a) Give unadjusted estimates and, if applicable, confounder-adjusted estimates andtheir precision (eg, 95% confidence interval). Make clear which confounders wereadjusted for and why they were included(b) Report category boundaries when continuous variables were categorized(c) If relevant, consider translating estimates of relative risk into absolute risk for ameaningful time period

Other analyses

17

Report other analyses done—eg analyses of subgroups and interactions, andsensitivity analyses
1Discussion
Key results

18

Summarise key results with reference to study objectives

Limitations

19

Discuss limitations of the study, taking into account sources of potential bias orimprecision. Discuss both direction and magnitude of any potential bias

Interpretation

20

Give a cautious overall interpretation of results considering objectives, limitations,multiplicity of analyses, results from similar studies, and other relevant evidence

Generalisability

21

Discuss the generalisability (external validity) of the study results

Other informationFunding

22

Give the source of funding and the role of the funders for the present study and, if
applicable, for the original study on which the present article is based*Give information separately for exposed and unexposed groups.
Note: An Explanation and Elaboration article discusses each checklist item and gives methodological background andpublished examples of transparent reporting. The STROBE checklist is best used in conjunction with this article (freelyavailable on the Web sites of PLoS Medicine at http://www.plosmedicine.org/, Annals of Internal Medicine at
http://www.annals.org/, and Epidemiology at http://www.epidem.com/). Information on the STROBE Initiative isavailable at www.strobe-statement.org.

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